ES2370855T3 - FUEL INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE. - Google Patents

Abstract

A fuel injection device for an internal combustion engine includes a housing and a valve element arranged within the housing. The valve element interacts with a valve seat lying in the region of a fuel outlet opening. It is proposed that at least one control piston and a nozzle needle of the valve element be coupled to one another via a hydraulic coupler. The hydraulic coupler has a coupling space and a non-return valve connected to the coupling space and which opens away therefrom.

Description

Fuel injection device for an internal combustion engine

State of the art

The present invention refers to a fuel injection device for an internal combustion engine 5, in accordance with the general concept of claim 1.

A fuel injection device is known in the market with which the fuel can be injected directly into a combustion chamber assigned for that purpose, from an internal combustion engine. Therefore, a valve element is disposed in a housing which, in the area of a fuel outlet orifice, has a surface under pressure that acts entirely in the direction of opening of the valve element. In

At the opposite end of the valve element, there is a control surface that acts in the closing direction, which delimits a control chamber. The control surface acting in the direction of closure, in its entirety is larger than the surface under pressure acting in the direction of opening when the valve element is open.

In the case of a closed fuel injection device, in a surface area under pressure that

15 acts in the opening direction, and on the control surface acting in the closing direction, there is a high fuel pressure that provides, for example, a fuel collection pipe (common rail). For the opening of the valve element, the pressure existing on the control surface is reduced until those resulting from the hydraulic force acting in the direction of opening on the surface under pressure exceed the force acting in the direction of closure. In this way, the opening of the valve element occurs.

20 For the reduction of the amount of leakage in fuel injection devices, the two-part design of a valve element for opening and closing the inlet holes has already been recommended in WO 2007/012510 A1 of fuel, and both parts can be subjected to the high injection pressure supplied by the fuel manifold. In this class of fuel injectors, the surfaces that act in the direction of opening and in the direction of closing, are subjected to the same high pressure so that the closing spring

25 acting on the valve element fails to apply the closing force necessary for a rapid closure of the fuel outlet orifices.

From the patent DE 101 60 191 A1 a servo valve with a first valve piston and a second valve piston which are coupled for actuation by means of a coupling chamber is known. The coupling chamber is connected to a high pressure connection via a check valve, to

30 establish a pressure threshold up to which the coupling chamber can be filled with an amount that deactivates it. In this way, the deactivation amount is driven to the low pressure side without being wasted.

From US 2003/0116640 A1 a hydraulic pressure multiplier is known for a fuel injection device, in which there is an exhaust groove between a first major piston and a second

35 minor plunger. In addition, a check valve is used as a pressure maintenance valve, which prevents the exit of the fuel locked under high pressure.

Disclosure of the present invention

The object of the present invention is to improve a fuel injection device of the kind mentioned in the introduction, so that the closing force is increased for the closure of the needle of the

40 injector, and operate reliably.

Said object is solved by means of a fuel injection device with the characteristics of claim 1. The advantageous improvements of the present invention are mentioned in the related claims. In addition, the main features of the present invention are found in the description below and in the drawings. In addition, at this point it has been proven that the characteristics can also be

45 present in very different combinations from each other for the present invention, without explicitly indicating.

In the case of the fuel injection device, in accordance with the present invention, with the check valve provided, during the closing process in the high pressure chamber surrounding the distributor piston, a pressure greater than in the fuel chamber is produced. coupling In this way, a closing force acts on the distributor piston in the high pressure chamber, which is greater than the force acting on the distributor piston in the opening direction 50 in the coupling chamber. In addition, the coupling chamber can be discharged via the check valve after a closing process of the valve element. In this regard, the following is considered: When the valve element is open and the pressure is thus reduced in the chamber

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of coupling, due to the inevitable leaks hydraulic fluids enter the coupling chamber. This means that during the closing of the valve element, more fluid is found in the coupling chamber than before opening. The check valve provided, in accordance with the present invention, prevents that when the injector needle comes into contact with the valve seat, the distributor piston rests on a "fluid reservoir" which, prior to the opening of the valve element, does not existed In an unfavorable case, said fluid reserve would increase with each process of opening and closing the valve element, until an opening of the valve element is no longer possible. The reliability of the operation of the fuel injection device according to the present invention, notably the reproducibility of the initial and final states, is significantly improved by the check valve.

In a first advantageous refinement, it is recommended that a valve element of the check valve be subjected to the action of a spring in its closed position. On the one hand, by means of a spring of this class, the safety of the valve element is also guaranteed in the state of rest without pressure of the fuel injection device. On the other hand, a spring of this class allows the adjustment of a certain difference in opening pressure, which ensures a secure closure of the injector needle.

It is particularly advantageous when a valve element of the check valve has a maximum travel which allows a predetermined time interval between a closing and a successive opening of the valve element to be fulfilled. Mainly for multiple injections within a duty cycle, very short time intervals are required between closing and opening of the valve element. By limiting the maximum travel of the check valve element, it is ensured that the check valve can be closed quickly when the pressure in the hydraulic coupling chamber begins to decrease at the beginning of an opening process.

A groove between the distributor piston and a section of the housing that delimits the coupling chamber in relation to a high pressure chamber can be designed such that the opening of the injector needle is carried out in a delayed manner. In this way, the capacity of the fuel injection device, according to the present invention, to provide reduced volumes is improved. In the case of an opening displacement of the distributor piston, fluid enters the coupling chamber through the groove, which leads to a delayed reaction of the injector needle. During the closure, something different happens, when the distributor piston comes into contact with the injector needle at the latest, an immediate closure of the injector needle is forced.

The precision in the fuel injection and the reproducibility are refined again, when the opening of the connection channel leading to the high pressure chamber is shaped so as to reduce the pressure waves. In this way, the fact that the pressure waves in the high pressure chamber, due to their comparatively larger volume, play a minor role in said chamber is considered, which is not appropriate for the joining channel that has a volume comparatively reduced and for the pressure chamber immediately upstream of the valve seat. By a corresponding conditioning of the opening, the pressure waves generated in the high pressure chamber can be reduced or dampened, at least, in the direction of the junction channel. A simple option for this is to form the funnel-shaped opening. In this way, the interruption of the pressure waves generated in the opening is achieved.

Brief description of the drawings

A particularly preferred exemplary embodiment of the present invention will be explained in detail in connection with the accompanying drawings. The drawings show:

Figure 1 a schematic representation of an internal combustion engine, with a fuel injection device;

Figure 2 a schematic and partially cut away representation of the fuel injection device of Figure 1; Y

Figure 3 a detailed representation of an area of the fuel injection device of Figure 1.

Forms of Execution of the Present Invention

In figure 1, an internal combustion engine as a whole has the reference symbol 10. Said engine is mainly used for driving a motor vehicle not shown. A high pressure transport device 12 transports fuel from a fuel storage tank 14 to a fuel pressure tank 16 ("common conduit"). In said tank the fuel is stored, for example, diesel or gasoline, under a very high pressure. A plurality of fuel injection devices 20 that inject the fuel directly into the combustion chambers 22 assigned to said devices are connected in the common conduit 16. Injection devices

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Fuel 20 also respectively has a low pressure connection 24, whereby they are connected to a low pressure zone, mainly with the fuel storage tank 14.

As seen in FIG. 2, the fuel injection device 20 comprises a housing 26 with an injector body 28, a main body 30 and an end body 32. In the housing 26 in its longitudinal direction a notch 34 is arranged in stepped form, in which a needle-shaped valve element 36 is housed. Said element is made up of two parts: By a distributor piston 38 and an injector needle 40.

The needle of the injector 40 has surfaces under pressure 42 that delimit a pressure chamber 44, and its resultants of hydraulic force are directed in the direction of opening of the needle of the injector 40. At its lower end in Figure 2, the needle of the injector 40 acts in a manner not shown in detail in Figure 2, together with a valve seat on the side of the housing (without reference symbol). In this way, the fuel outlet orifices 46 can be found separated from the pressure chamber 44, or connected to said chamber. The needle of the injector 40 has a section 48 with a smaller diameter, and a section 50 with a larger diameter. With section 50, the needle of the injector 40 is driven into the body of the injector 28 by a longitudinal displacement.

The distributor piston 38 is housed in the main body 30. An upper end zone of the distributor piston 38 in Figure 2 is shaped as a guide that is housed and driven in the final body 32. A spring 52 is supported by a shoulder in the distributor piston 38, formed by an annular flange (without reference symbol), and said spring acts in the direction of closure. The upper axial end surface in Figure 2 of the distributor piston 38, forms a hydraulic control surface 54 that acts in the direction of closing of the valve element 36. Said surface delimits together with the final body 32 a hydraulic control chamber 56.

The control chamber 56 is connected by an intake butterfly valve 58 in the final body 32, with a high pressure chamber 60 which, due to its large volume, can also be referred to as a storage chamber, and which is connected with a high pressure connection 18. On the other hand, the control chamber 56 is connected by an outlet butterfly valve 62 which is incorporated in the final body 32, with an electromagnetically operated 2/2 way switching valve 64. According to the switching position, said valve connects or blocks the outlet throttle valve 62 towards the low pressure connection 24. In addition, the high pressure chamber 60 is connected to the pressure chamber 44 via a connection channel 66, in a way yet to be represented.

Between the injector body 28 and the main body 30, a disk-shaped guide member 68 is embedded. Its precise construction results from Figure 3: Next, the guide element 68 comprises a through hole in stepped form (without reference symbol), whose upper area in Figure 3 forms a guide section 70. In said section a bottom end zone 72 in figures 2 and 3 of the distributor piston 38, in the sliding adjustment. The diameter of the end zone 72 is somewhat larger than the diameter of the section 50 of the needle of the injector 40, however, it is smaller than the diameter of the distributor piston 38 in that area leading into the final body 32. Such proportions of the diameters are important for the operation of the fuel injection device 10. In Figure 3 it can be seen that the distributor piston 38 has an end pin 74 below the end zone 72, whose diameter is smaller than that of the end zone 72 and it is also smaller than the area of the needle of the injector 40 adjacent to the distributor plunger 38. Approximately at the axial height of said end pin 74, an annular flange 76 extends radially inwardly from the through hole in the guide member 68. circumferential that forms a stop for the needle of the injector 40, since its inner diameter is smaller than the outer diameter of the final area of the needle of the injector 40 adjacent to said flange. However, the stop 76 is not required.

The annular chamber formed between the end pin 74, the end zone 72, the injector needle 40 and the guide element 68, is called coupling chamber 78. Said chamber is part of a hydraulic coupler 80, as explained in detail a then, by means of which the movements of the distributor piston 38 and the injector needle 40 are coupled together. The hydraulic coupler 80 also comprises a check valve 82 with a valve element 84 formed as a sphere, which in a position of The closure is subjected to the action of a valve spring 86. In the open state, the check valve 82 connects the hydraulic coupling chamber 78 with the high pressure chamber 60. The check valve 82 is designed to open from the coupling chamber 78 towards the high pressure chamber 60.

A section of the connection channel 66 that is arranged in the guide element 68 comprises a butterfly valve that regulates the flow 88. An opening area 90 of the connection channel 66 leading to the high pressure chamber 60 is formed in funnel shape.

The fuel injection device 20 operates as follows: In the initial state, when the switching valve 64 is out of current, the hydraulic control chamber 56 is separated from the low pressure connection 24, and connected to the high pressure connection 18 via the throttle valve

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intake 58 and, therefore, with the common conduit 16. Therefore, in the hydraulic control chamber 56 there is the same pressure as in the high pressure chamber 60. Said pressure predominates in the initial steady state also in the chamber of pressure 44 through the connecting channel 66. Due to a certain leak between the guide section 70 of the guide element 68 and the final area 72 of the distributor piston 38, as well as the leaks between the needle of the injector 40 and the body of injector 28 in section 50, said pressure also exists in the coupling chamber 78. Overall, in this configuration a force is generated that acts in the direction of closing of the valve element 36, which presses said element against the valve seat in the area of the fuel outlet holes 46.

When the switching valve 64 is supplied with current, the outlet butterfly valve 62 is connected with the low pressure connection 24. In this way, the pressure in the hydraulic control chamber 56 is reduced. On the contrary, in the chamber of coupling 78 the initial high pressure still predominates. Therefore, together a force is produced that acts on the distributor piston 38 in the direction of opening. Therefore, said force begins to move upwards in the opposite direction to the force of the spring 52, as indicated in Figures 2 and 3. In this way, by increasing the volume the pressure in the coupling chamber 78 decreases , while in the pressure chamber 44 the initial high pressure still predominates. Together, a force also acts that acts on the needle of the injector 40 in the opening direction, due to which the needle of the injector 40 begins to move upwards as in Figures 2 and 3, that is, it rises from its valve seat in the area of the fuel outlet orifices 46. In this way, fuel can be injected from the common conduit 16 through the high pressure connection 18, the high pressure chamber 60, the connection channel 66, the pressure chamber 44 and through the fuel outlet orifices 46 towards the combustion chamber 22. Due to the butterfly valve that regulates the flow 88 in the joint channel 76, the pressure chamber 44 is generated also a lower pressure than in the high pressure chamber 60.

Since also in the coupling chamber 78, at least temporarily less pressure prevails than in the high pressure chamber 60, a certain amount of fuel is conducted through the guide groove between the guide section 70 and the area end 72, from the high pressure chamber 60 and between the injector needle 40 and the injector body 28 in section 50, from the pressure chamber 44 to the coupling chamber 78. By controlled sizing of the guide groove mentioned, the amount of fuel circulating from the high pressure chamber 60 to the coupling chamber 78 can be regulated, which first allows a controlled regulation of the opening behavior of the valve element 36. The larger the guide groove is , the pressure in the coupling chamber 78 decreases more "dampened", and the needle of the injector 40 reacts more delayed. This is useful mainly when it is required that the fuel injection device 20 be able to also inject small amounts of fuel.

To terminate an injection, the switching valve 64 is returned to its closed position, in which the union of the hydraulic control chamber 56 with the low pressure connection 24 is blocked. By the intake throttle valve 58, the pressure in the hydraulic control chamber 56 is increased. In this way, the distributor piston 38 moves again in the closing direction, since the pressure in the coupling chamber 78 is lower than in the hydraulic control chamber 56. Then, the pressure in the coupling chamber 78 increases again due to the reduction in volume, which ultimately together generates a force acting on the needle of the injector 40 in the direction of closing of said needle. The displacement of the needle of the injector 40 comes to an end when said needle is supported with its lower end of Figure 2, again in the valve seat on the side of the housing and, thus, fuel can no longer escape through of the fuel outlet orifices 46. Since in the meantime fuel is driven, as mentioned above, from the high pressure chamber 60 and from the pressure chamber 44 to the coupling chamber 78, the distributor piston 38 at the end of its closing movement stops with a "fuel reserve", which leads to a dynamic increase in the pressure in the coupling chamber 78, achieving a pressure that is greater than the pressure in the high pressure chamber 60. Next, the check valve 82 is opened so that the fuel entering the coupling chamber 78 can escape into the high pressure chamber 60. Therefore, at the end of its displacement of c ierre, the distributor piston 38 comes into contact again with the needle of the injector 40.

In the event that the fuel injection device 20 must inject fuel by means of a plurality of successive brief injections to each other, the valve element 36 must be able to be opened again, immediately after having reached its closed position. To do this, after “excess” fuel present in the coupling chamber 78 has been conducted through the check valve 82 towards the high pressure chamber 60, the coupling chamber 78 is required as quickly as possible again a closed volume which engages the needle of the injector 40 in the opening displacement of the distributor piston 38. This is achieved as long as the travel of the valve element 84 of the check valve 82 is limited to a very reduced maximum travel. In the event that the pressure in the coupling chamber 78 decreases again due to an opening displacement of the distributor piston 38, the valve element 84 should only travel a reduced path, until said element is again in its closed position and, in this way, the coupling chamber 78 can form a closed volume.

The conditioning of the opening area 90 of the connecting channel 66, in the form of a funnel that extends

towards the high pressure chamber 60, it has as a consequence the following effect: Due to the opening and closing

of the valve element 36, in the high pressure chamber 60 pressure oscillations occur which, without

However, they cannot be perceived there due to the size of the high pressure chamber 60. However, the channel of

5 junction 66 and the pressure chamber 44 have a considerably smaller volume than in the high chamber

pressure 60, so that there the pressure fluctuations impact intensely and, in this way,

injection accuracy is reduced. At this point, the funnel shaped opening area 90 acts

in the following way: Through this zone they “dissipate” or, the pressure waves that occur are reduced

in the opening zone 90, so that the pressure fluctuations are only transmitted in a reduced way to the junction channel 66. Therefore, the fuel can be dosed with a particularly high precision,

by means of the fuel injection device 20 presented here.

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Claims (6)

one.

Fuel injection device (20) for an internal combustion engine (10) with a housing (26) and a valve element (36) disposed in the housing (26), which acts together with a valve seat arranged in the area of at least one fuel outlet orifice (46), wherein at least one distributor piston (38) and an injector needle (40) of the valve element (36) are coupled together by a coupler hydraulic (80), where an annular chamber is formed between an end pin (74) and an end zone (72) of the distributor piston (38), of the injector needle (40) and of a guide element (68) forming a coupling chamber (78) for the hydraulic coupler (80), wherein the distributor piston (38) has a hydraulic control surface (54) acting in the direction of closing of the valve element (36), which together with an end body (32) of the housing (26) it limits a hydraulic control chamber (56), where the chamber The control valve (56) is connected by an intake throttle valve (58) in the final body (32), with a high pressure chamber (60) that is connected to a high pressure connection (18), and by means of an outlet butterfly valve (62) in the final body (32) it is connected with an electromagnetically operated 2/2 way switching valve (64), which according to the switching position connects or blocks the valve from the outlet butterfly (62) to a low pressure connection (24), and where a connecting channel (66) is provided that leads from the high pressure chamber (60) to the valve seat arranged in the area of the fuel outlet port (42), wherein the coupling chamber (78) comprises a check valve (82) connected to said chamber, which in the open state connects the coupling chamber (78) with the high pressure chamber (60), such that the valve retention (82) open from the coupling chamber (78) to the high pressure chamber (60).

2.

Fuel injection device according to claim 1, characterized in that a valve element (84) of the check valve (82) is subjected to the action of a spring (86) in its closed position.

3.

Fuel injection device according to claim 2, characterized in that the valve element (84) of the check valve (82) has a maximum travel which allows to meet a predetermined time interval between a closing and a successive opening of the valve element (36) of the fuel injection device (20).

Four.

Fuel injection device according to one of the preceding claims, characterized in that a groove (70) between the distributor piston (38) and a section of the housing (70) delimiting the coupling chamber (78) in relation to a High pressure chamber (60), is designed in such a way that the opening of the injector needle (40) is carried out in a delayed manner.

5.

Fuel injection device according to claim 1, characterized in that an opening area (90) of the junction channel (66) leading to the high pressure chamber (60) is shaped so as to reduce pressure waves .

6.

Fuel injection device according to claim 5, characterized in that the opening area (90) has a funnel shape.